Method of producing films in natural color



July 30, 1935. l w T. cREsPlNl-:L 290091589 METHOD `OF PRODUCING FILMSIN NATURAL COLOR Filed Aug. 19, 1950 f//ff/ ,C h l; @ed fg/@Mg.Secondary Ema/Sion 6 E Remo l/a/ of Ex'cess Rea Jc/e wvo/MASK YPatented July 30, 19.35

METHOD OF PRODUCING FILMS IN NATURAL COLOR William T. CrespneL LosAngeles, Calif., assignor, by mesne assignments, to Hughes IndustriesC`o. Ltd., a corporationof Delaware Application August 19, 1930, SerialNo. 476,251

22 Claims.

My invention relates to`a methodof producing films in natural color,employing a positive rlhn vhaving two layers of sensitized emulsionsuperimposed on one side thereof, this film being termed a sandwichillm.

It is an object of my invention to provide a process for producing acolor positive in which the image appears in natural color, and it is afurther object of the invention to provide a process which will givesatisfactory or substantially perfect results in the production of acolor lm without the exercise of extreme care in the performance of theprocess.

It is a further object of the invention to provide a process of theabove character by which a color iilm may be vproduced from color valuenegatives ina minimum period of time and with a relatively smallexpenditure of labor.

Further objects and advantages of'my invention ywill appear throughoutthe disclosure of a preferred manner of performing my new process, whichrefers to the accompanying drawing diagrammatically showing myinvention.

For the purpose of segregating the principal steps of my invention, Ishall in the drawing and hereinafter in the description designate sameby letters.

(A) Preparation of color value negatives In my process I prefer toemploy color value negatives representing yellow-red and blue-greenvalues of a color image. Owing to the fact that ,there are many methodsknown to the art of color photography for the production of color valuenegatives, and since this invention relates principally 'to a newprocess for producing a positive film in color, it is not necessary tofurther describe the production of the color value negatives employed inthe process.

Although other types of lm may be employed in the practice of myinvention, I prefer to use the type of lm III shown in the diagrammaticdisclosure of step B of my invention, which consists of a transparentbase, .generally of celluloid, a thin primary gelatine substratum on thefront face of the transparent base, a primary layer of sensitizedemulsion, a secondary gelatine substratum, and an outer or secondarylayer of sensitized emulsion.v 'I'he primary substratum has itsprincipal utility in securing the primary sensitized emulsion to thetransparent base, and the secondary'substratum serves to separate and toact as' 'a barrier between the primary and secondary sensitized emulsioncoatings. Incorporated either in the emulsions or in the secondarysubstratum of the positive film I0 is a yellow dye whichpreventspenetration of light from one emulsion to the other.

(B) Printing positives from color value negatives In the printing of thepositive l0, the red color value negative is placed adjacent to thetransparent base, and the primary sensitized emulsion is printed bylight which passes through the red color value negative, the transparentbase, and the primary gelatine substratum. The blue color value negativeis placed adjacent to the secondary sensitized emulsion, and thesecondary sensitized emulsion is printed directly from the blue colorvalue negative. The printing of the primary and secondary sensitizedemulsions may be carried on simultaneously or separately. y

In printing I find it advisable to diilerentiate between the voltageused in printing the outer and inner emulsions. To clarify this I woulduse volts to the outer or secondary emulsion and volts to the inner orprimary emulsion. The reason for this is that it is an advantage indeveloping, since the developer attacks more readily the outer image andhas to penetrate through to the inner image, during which time the outerimage is still developing, but because of the additional exposure to theinner emulsion it will develop more quickly when the developer hasthoroughly saturated it.

(C) Developing, fixing, and washing positive This step of the process Icarry on in the usual manner of developing photographic positives andhave used with satisfactory results a number of developers, preferenceamong which is given to Amidol developer, which produces so-called atimages, although vgood results may also be obtained from standarddevelopers, such as East-A man developer No. 16. After treatment by thedeveloper solution, the image is fixed and then thoroughly washed,whereupon the next step of vthe process may be carried on with the lmwet or with the lm dried.

' `(D) -Hordanting secondary emulsion `Although it is possible tocontinue the operation andA perform the operation of mordanting theouter or secondary emulsion while the film is still wet, I ilndthat ifthe illm is iirst dried thoroughly, the coloring operations may becarried on to best advantage. The positive film is conducted through abath or solution of potassium tri-iodide and potassium iodidecharacteristics with an addi- 'r tion of acetic acid. A suitable formulafor the mordant for basic dyes which I employ in this step of theprocess is as follows:

Iodine resublimated 2 grams Potassium.iodide 25 grams Acetic acid(glacial) 50 c. c. of 10% solution Water to make 500 c. c.

The lm is allowed tol remain in this solution for a period of timesufficient to penetrate through and bleach the surface image orsecondary sensitized emulsion. The secondary gelatine substratumseparatingthe two layers of emulsion acts as a retardant to themordanting solution and will prevent the mordantiing solution fromentering the silver image of the primary sensitized emulsion. If theexposure and development are carefully adjusted, I nd that thisoperation may be consistently performed without affecting the image ofthe primary sensitized emulsion in a time of approximately one andone-half minutes. The film is then run into a wash tank of running waterto thoroughly wash out the excess of mordanting solution. The abovemordanting formula is the preferred proportion, but I have found thatthe proportions may be considerably varied without greatly aecting theresults obtained. The potassium iodide is the predominating chemicalemployed, and the potassium tri-iodide and acetic acid are the ancillarychemicals. I find that the following proportions may be satisfactorilyemployed:

Iodine resublimated 1 1/4 to 2 grams Potassium iodide 25 to 50 gramsAcetic acid 50 to 100 c. c. of 10% solution Water to make 500 c. c.

(E) Arrestz'ng of mordantng action From the wash tank of the previousstep of the process the film is carried into a solution of an arrestingagent of bisulphite character, such as either potassium metabisulphiteor sodium bisulphite, good results being obtained where a 10% solutionis employed. In this solution the action of the mordanting solution isimmediately stopped, and the mordanting solution is cleared from thefilm. 'I 'his operation requires from one-half minute to one minute,depending upon the strength of the arresting solution. The film is againthoroughly washed in a bath of running water to remove the clearing orarresting solution.

(F) Red-dyeing of secondary emulsion I SafranineY 1 gram in 100 c. c. ofwater Chrysoidine Y 1 gram in 100 c. c. of water From thisstock/solution I prepare the red-dyeing bath in the followingproportions:

chrysoidine Y 9o c. c. Safranine Y 10 c. c. Acetic acid 1 c. c.

Where this solution is made in accordance with the above formula, thered-coloring action may be accomplished by running the film into thebath thereof for a period of approximately three minutes, during whichtime the mordant absorbs the basic dye and becomes or is converted intoa brilliant orange-red.

(G) Removal of excess red-dye The film is now carried into running waterwhich removes the excess vred-dyeing solution from the film, leaving thesilver deposit forming the image of the secondary emulsion coloredorange-red, the strength of the color being in proportion to thequantity of the silver deposit. If the correct dyes are used and intheir correct proportions, substantially as noted above, this removal ofthe excess red-dye will take approximately ve minutes. At this time thefilm carries a top'image with a basic red dye and a lower image in theprimary sensitized emulsion which is still black and white, the twoimages being separated by the intermediate substratum.

(H) Blue-toning primary Aemulsionr vsolution of low acid content. I findthat great care must be exercised in the use of the more potent acids,such as hydrochloric acid, which .affect the iodide mordant so as toincrease the opacity of the red-dye image, which, if correctly executed,is very transparent. For this purpose I prefer to use a ferrie bath inwhich acetic acid is substituted for the usual hydrochloric acid, the

ferrie bath being made substantially in accordance with the followingformula:

Ammonium persulphate 31/2 grams Ferric alum 21/2 grams Ferricyanide241/2 grams Acetic acid 10 c. c. of 10% solution Water to make 1000 c.c.

This bath will not affect the red-dye image of the secondary emulsionbut will readily penetrate through the secondary substratum and in fouror five minutes convert the image of the primary substratum to ablue-tone image. After being subjected to the ferrie solution for alength of time gauged in accordance with the strength of the solution,the film is again washed in running water. f

(I) Clearing or firing the blue-teme primary emulsion Y Since the reddyed image is relatively transparent and the ferrie image is somewhatopaque, it is necessary to fix the ferrie image to bring itstransparency into a suitable balance with the red-dye image. However,the ordinary hypo fixing bath cannot be used for this purpose since itdestroys the silver iodide mordant so as to result in release of the reddye from the image of the secondary emulsion. For the purpose of fixingthe ferrie image I employ a 10% solution of potassium iodide. Since themordanted image of the secondary emulsion is composed of silver iodide,this fixing solution has no effect upon `the red-dye image but willeffectively clear the blue image of the primary emulsion in a period ofabout three minutes, after which the film is again washed. An addedadvantage of the use of this bath is the fact that if it were possibleto use a hypo sulphite fixing solution, a prolonged washing would thenbe necessary to remove all traces of hypo from the lxn itself, and

i Water this prolonged washing would impair both of the colored images.Thus, where the iodide clearing solution is used, a brief wash oi' fromtwo to four minutes is suilicient and completes the operation ofproducing the positive film in color.

If a sound track is to be printed on the positive film, I find itadvisable to-'print such sound track by placing the sound negativeagainst the secondary emulsion and to print same with greater lightexposure than that used in the printing of the red image, ln order thatthe light will penetrate and also expose the sound track portion of theprimary emulsion. y

A transparent dyed image is not a suitable medium for sound recordingbecause the rays from the exciter lamp, which is part of the projectorequipment, will readily penetrate the dyed image, and the resultingsound would be very weak and poor in quality. The sound track could be,of course, suitably protected by a varnishing solution, leaving it in ablack and white condition, but as this adds greatly to the cost ofproduction, it is an operation to avoid. Therefore, as alreadyexplained, I prefer to print the sound to a density which will penetrateboth the top and bottom emulsions. Consequently, when the film iscompletely colored, the sound track is composed of both red and blue.'I'hese colors, V being superimposed, give the sound track an appearanceof more or less opaque strlations on a transparent base.

In order to clearly disclose a preferred embodiment of my invention, Ihave hereinbefore confined the process to use with the red color imageon the outside of the film or in the secondary sensitized emulsion. Itwill be perceived that in the foregoing I have clearly disclosed aprocess wherein the image of the secondary emulsion or outer emulsion isfirst mordanted and then dyed. and the underneath or primary sensitizedemulsion is then toned or converted to the desired color without in anyway affecting the image in the outer or secondary sensitized emulsion.Although I have hereinbefore disclosed the red image on the secondaryemulsion and the greenblue image on the primary emulsion, this order orplacingmay be reversed. The green-blue image may be imprinted in theouter or secondary emulsion, and the 'orange-red image may be imprintedthrough the film IB and in the primary or inner sensitized emulsion. Inso doing, the principal steps of the process are adhered to. The outeremulsion is first mordanted and then dyed with a blue-green basic dye,-after which the inner or primary emulsion is converted to a red color.

The outer image may be mordanted by subjecting it to a solution havingsubstantially the following proportions, in which potassium iodide isthe principal chemical:

Iodine Potassium iodide Acetic acid 3 grams 25 grams y 4 grams 2000 c.c.

. may be accomplished in apln-oximatelyA five minutes, after which thefilm is passed through running water to clear the highlights. The innerimage is then red-toned by use of a uranium toning bath, which may bemade up in accordance with the following formula:

Potassium oxalate 5 grams Uranium nitrate 5 grams Potassium ferricyanide5 grams Hydrochloric acid 2c.c.

Water 1000 c. c.

If it is necessary to print a sound record on this color positive, suchsound record is printed after step B, or at the time indicated at B inthe drawing, from the front or surface of the film and not through theback. In printing I do not confine the sound record necessarily to thesurface emulsion but simultaneously print the primary or inner emulsionsin order that the final colored sound record will be represented in bothred and green and will therefore approach very near to black and white.

In the foregoing description I have set forth the process in what Ibelieve to be its most practical form. I nd, however, that the steps ofthe process may be deviated from, Within reasonable limits, withoutseriously affecting the results to vbe obtained, and I contemplate thatfurther experience in the practice of the invention may developadvisable variations lying Within the scope of the process hereinabovefully explained.

I claim as my invention:

1. A method of producing a color positive from a film having a primarysensitized emulsion and a secondary sensitized emulsion in superposedrelation, comprising: printingv photographic images on said primary andsecondary emulsions respectively from red and blue color valuenegatives; developing said images; mordanting the film; blue-toning saidprimary emulsion by appli-v cation thereto of a blue-toning solutioncontaining ferrie salts and having no affinity for the mordant -carriedin said secondary emulsion; andclearing said primary emulsion to renderthe blue-toned image thereof more transparent, by subjecting the film toa solution of potassium iodide.

2. A method of producing a color positive from a film having a primarysensitized emulsion and a secondary sensitized emulsion in superposedrelation, comprising: printing photographic images on said primary andsecondary emulsions respectively from redsand blue color valuenegatives; developing said images; mordanting the image of saidsecondary emulsion for a basic dye by use of a solution having potassiumiodide as its principal constituent; arresting the action of the mordantby subjecting it to a bisulphite solution; applying red basic dye tosaid secondary emulsion; removing excess of red dye from said film;blue-toning said primary emulsion by application thereto of ablue-toning solution containing ferric salts and having no ainity forthe mordant carried in said secondary emulsion; and clearing saidprimary emulsion to render the blue-toned image thereof moretransparent, by subjecting the film to a solution of potassium iodide.

3. A method oi' producing a color positive from a lm having a primarysensitized emulsion and a secondary sensitized emulsion in superposedrelation, comprising: printing photographic images on said primary andsecondary emulsions respectively from red and blue color valuenegatives; developing said images; mordanting the image of saidsecondary emulsion for a basic dye by use of a solution having potassiumiodide as its principal constituent; arresting the action of themordantl by subjecting it to a bisulphite solution; applying red basicdye to said secondary emulsion; blue-toning said primary emulsion byapplication thereto of a blue-toning solution containing ferric salts;and clearing said primary emulsion to render the blue-toned imagethereof more transparent, by subjecting the film to a solution ofpotassium iodide.

4; A method of producing a color positive from a iilm consisting of atransparent base, a primary emulsion thereon, and a secondary emulsionover said primary emulsion in superposed relation, comprising: printingphotographic images on said primary and secondary emulsions respectivelyfrom red and blue color value negatives; developing said images;mordanting the image of said secondary emulsion for a basic dye;applying red basic dye to said secondary emulsion; blue-toning saidprimary emulsion by application thereto of a blue-toning solutioncontaining ferric salts and havingno afiinity for the mordant carried insaid secondary emulsion; and clearing said primary emulsion to renderthe blue-toned' image thereof more transparent by' subjectingthe lm to asolution'containing an iodide.

5. A method of producing a color positive from a lm consisting of atransparent base, a primary emulsion thereon, and a secondary emulsionover said primary emulsion in superposed relation, comprising: printingphotographic images on said primary and secondary emulsions respectivelyfrom red and blue color value negatives; developing said images;mordanting the image of said secondary emulsion'for a basic dye by useof a solution having potassium iodide as its principal constituent;arresting the action of the mordant by subjecting it to a bisulphitesolution; applying red basic dye 4to said secondary emulsion; removingexcess of red dye from said film; blue-toning said primary emulsion byapplication thereto of a blue-toning solution containing ferrie saltsand having no ailinity for the mordant carried in said secondaryemulsion; and clearing said primary emulsion to render the blue-tonedimage thereof more transparent, by subjecting the lm to a solution ofpotassium iodide.

6. A method of producing a color positive from a lm consisting of atransparent base, a primary emulsion thereon, and a secondary emulsionover said primary emulsion in superposed relation, comprising: printingphotographic images on said primary and secondary emulsions respectivelyfrom red and blue color value negatives; developing said images;lmordanting the image of said secondaryemulsion for a basic dye bysubjecting same to a solution of substantially two grams oi' iodine,twenty-five grams of potassium iodide, and ftycubic centimeters of 10%solution of acetic acid, together with suiiicient water to make a totalof five hundred cubic centimeters of mordanting solution; applying redbasic dye to said secondary emulsion; removing excess of red dye fromsaid-film; blue-toning said primary emulsion by application thereto of ablue-toning solution having no ainity for the mordant carried in saidsecondary emulsion; and clearing said primary emulsion to render theIblue-toned image thereof more transparent.

7. A method of producing a color positive from a film consisting of atransparent base; a primary emulsion thereon, and a secondary emulsionover said primary emulsion in superposed relation, comprising: printingphotographic images on said primary and secondary emulsions respectivelyfrom red and blue color value negatives; developing said images;mordanting the image of said secondary emulsion for a basic dye bysubjecting same to a solution of substantially two grams of iodine,twenty-five grams of potassium iodide, and fifty cubic centimeters of10% solution of acetic acid, together with suilicient water to make atotal of five hundred cubic centimeters of mordanting solution; applyingred basic dye to said secondary emulsion, said red basic dye includingsubstantially nine parts of chrysoidine Y, one part of safranine Y, anda small amount of acetic acid added thereto; removing excess o red dyefrom said iilm; bluetoning said primary emulsion by application theretoof a blue-toning solution having no afnity for the mordant carried insaid secondary emulsion; and clearing said primary emulsion to renderthe blue-toned image thereof more transparent.

8. A method of producing a color positive from a film having a primarysensitized emulsion and a secondary sensitized emulsion in superposedrelation, comprising: printing photographic images on said primary andsecondary emulsions respectively from red and blue color valuenegatives; printing a single sound track through the cooperating edgeportions of both of said emulsions to form identical and superimposedsound-representing images in said primary and secondary emulsions which,when subsequently toned red and bluefwill produce black striations alongthe sound track of the positive lm; developing said images; mordantingthe image of said secondary emulsion for a basic dye; 'applying redbasic dye to said secondary emulsion; removing excess of red dye fromsaid iilm; bluetoning said primary emulsion by application thereto of ablue-toning solution containing ferri salts and having no ainity for themordant carried in said secondary emulsion; and clearing said primaryemulsion With a solution of soluble iodide to render the blue-tonedimage thereof more transparent. v

9. A method of producing a color positive from a lm having a primarysensitized emulsion and a secondary sensitized emulsion in superposedrelation, comprising: imprinting said primary and secondary emulsionsrespectively with cooperating images; developing said images; mordantingthe image of said secondary emulsion to receive a dye; applying a dye tosaid secondary emulsion; subjecting said lm to a toning solutioncontaining erric salts to convert the image of said primary emulsion ytoa desired color; and clearing said primary emulsion by subjecting the lmto an iodide-containing solution.

10. A method of producing a color positive from a film having a primarysensitized emulsion and a secondary sensitized emulsion, comprising:imprinting said primary and secondary emulsions respectively with'cooperating images;

imprinting a sound track simultaneously through.

lsion to receive a dye; applying a dye to said secondary emulsion; andthen converting the image 'of said primary emulsion to a desired color rtone.

11. A method of producing a color positive from a film having a primarysensitized emulsion and a secondary sensitized emulsion, comprising:imprinting said primary and secondary emulsions respectively withcooperating images; imprinting a sound track simultaneously through bothof said emulsions so that superimposed identical sound track images willbe impressed on both of said emulsions; developing said images;mordanting the image of said secondary emulsion to receive a dye;applying a dye to said secondary emulsion; and subjecting said illm to atoning solution to convert the image of said primary emulsion to adesired color.

12. A method of producing a sound track in a color positive havingprimary and secondary sensitized emulsions, comprising: imprinting saidprimary and secondary emulsions respectively with cooperating colorvalue images; imprinting a sound track simultaneously in both of Vsaidemulsions so that superimposed identical sound track images will beimpressed on both of said emulsions; developing the images contained insaid emulsions; and subsequently changing the images of said emulsionsfrom black and white character to complementary colored images.

13. A method of producing a sound track in a color positive havingprimary and secondary sensitized emulsions, comprising: imprinting saidprimary and secondary emulsions respectively with cooperating colorvalue images; from a single sound record imprinting a sound track.

through both of said emulsions so that superimposed and identical soundtrack images will be impressed simultaneously on both of said emulsions;developing the images contained in Asaid emulsions; and subsequentlychanging the irnages of said emulsions from black and white character tocomplementary colored images.

14. A method of producing a color positive from a iilm having a primarysensitized emulsion and a secondary sensitized emulsion inl superposedrelation, comprising: imprinting said primary and secondary emulsionsrespectively with cooperating images; developing said images; mordantingtheI image of said secondary emulsion to receive a dye; applying a dyeto said secondary emulsion; subjecting the film to a toning solutioncontaining ferrie salts; and clearing said primary emulsion bysubjecting the film to an iodide-containing solution. y

15. A method of producing a color positive from a' lm having an emulsionstructure thereon of sufficient thickness to be divided-into inner andouter layer portions, comprising: printing complementary photographicimages on said inner and outer portions oi said emulsion; developingsaid images; mordanting the image o! said outer portion for a basic dye;pplyin red basic dye to said outer portion; blue-toning said innerportion of said emulsion by Aapplicationthereto of a blue-toningsolution containing ferric salts; and clearing said inner portion bysubjecting the iilm to a solution of potassium 4iodide.

16. A method of producing acolor positive from a lm having an emulsionstructure thereon of suiilcient thickness to be divided into inner andouter layer portions, comprising: printing.y

complementary photographic 'images on said inner and outer portions ofsaid emulsion; developing said images; mordanting the image of saidouter portion for a basic dye by use of a solution having potassiumiodide as its principal constituent; arresting the action of the mordantby subjecting it to a bisulphite solution; applying red basic dye tosaid outer portion; blue-toning said inner portion lof said emulsion byapplication thereto of a blue-toning solution containing ferric salts;and clearing said inner portion by subjecting the illm to a solution ofpotassium iodide.

17. A method of producing a color positive from a lm having an emulsionstructure thereon of suilicient thickness to be divided into inner andouter layerportions, comprising: printing complementary photographicimages on said inner and outer portions of said emulsion; developingsaid images; mordanting the image of said outer portion for a basic dye;applying basic dye to said outer portion; toning said inner portion ofsaid emulsion by application thereto of a toning solution containingferrie salts; and clearing said inner portion by subjecting the iilm toa solution of potassium iodide.

18. A method of producing a color positive from a film, having anemulsion structure thereon of suiiicient thickness to be divided intoinner and outer layer portions, comprising: printing complementaryphotographic images on said inner and outer portions of said emulsion;developing said images; mordanting the image of said outer portion for abasic dye by use of a solution having potassium iodide as its principalconstituent; arresting the action of the mordant by subjecting it to abisulphite solution; applying basic dye to said outer portion; toningsaid inner portion of said emulsion by application thereto of a toningsolution containing ferrie salts; and clearing said inner portion bysubjecting the lm to a solution of potassium iodide.

v19. A method of producing a color positive from a iilm having anemulsion structure thereon of suirlcient thickness to be divided intoinner and outer layer portions, comprising: printing complementaryphotographic images on said inner and outer portions of said emulsion;imprinting a sound image simultaneously through both said inner andouterportions so that such sound image will be impressed in both inner andouter portions of said emulsion; developing said images; mordanting theimage of said outer portion for a basic dye; applying red basi'c dye tosaid outer portion; blue-toning said inner portion of said emulsion byapplication thereto of a blue-toning solution containing ferric salts;and clearing said inner portion by subjecting the lm to a solution ofpotassium iodide.

j 20. The method of producing a color photograph which includes:producing two superposed images in a photographic emulsion; developingsaid images; coloring the outer of said images a certain color; toningthe inner of said images a substantially complementary color; andclearing said images with a solution containing potassium iodide.

21. The step in color toning a photograph which consists of clearingsaid toned photograph with a solution containing potassium iodide.

' 22. A method of producing a. color positive from a illm having anemulsion structure thereon of suflicient thickness to be divided intoinner and 'outer layer portions, including; printing superimposedcomplementary color value images in said inner and outer portions ofsaid emulsion; developing said images; mordanting the outer image for abasic dye; applying a blue to green basic dye to said outer image; redtoning said'inner image with a solution containing a uranium salt; andclearing 'saidinner image with a solution containing potassium iodide.

WILLIAM T. CRESPINEL.

